ERYTHRODEXTRIN, ACHROODEXTRIN, GRENZDEXTRIN, ETC. 133 



present. Pottevin states tliat the dextrins differ only physically, and that the denser parts 

 of the starch-grains yield a dextrin more difficult to saccharify than the other parts. 



A reversion product was obtained by Syniewski (Bcr. d. d. chem. Gesellsch., 1898, 

 XXXI, 1791) in his experiments with soluble starch obtained by the action of sodium 

 peroxide, which he beUeves is probably identical with a substance formed by the action 

 of high pressure on potato starch. He noted that solutions containing more than 12.5 

 per cent of soluble starch deposit a wliite precipitate that is insoluble in cold water, and 

 which when washed with water, alcohol, and ether, showed upon analysis that it is a deriva- 

 tive from soluble starch by the removal of water. In a later communication (Ann. d. 

 Chem. u. Pharm., 1899, cccix, 282) he holds: 



(1) The starch-grains consist of a homogeneous substance having the formula C'uHioOj. 



(2) That two forms of hydrolysis occur, carbinolhydrolysis and carbonylhydi'olysis, accord- 



ing as when in the combination with water there goes into solution an auhychid union 

 between two cai-binol groups, or between two groups, one of which is carbonyl. 



(3) That the products from potato starch which do not reduce Fehling's solution are the 



results of carbonj'lhydrolysis. 



(4) That the simplest product of carbinolhydrolysis is amylogen (C54H96O48), and that the 



starch-molecule, as well as products of carbinylhydrolysis between starch and amy- 

 logen, consists of an unkno^^^^ number of amylogen molecules in some form of an 

 anhydrid miion. 



(5) That amylogen consists of 3 maltose groups in combination with 1 dextrin residue contain- 



ing 18 atoms of carbon, and that the latter is composed of 3 sugar residues, of which 2 

 are isomaltose residues. 

 (G) That during the first stage of the hydrolysis of amylogen the maltose molecules gradu- 

 ally separate, and the dextrin residue remains behind, but that this finally splits into 

 isomaltose and glucose, and the isomaltose finally into glucose. 



(7) That the diastatic hytholysis of amylogens gives rise to intermediate products, the different 



stages being expressed as follows: amylogen = dextrin residue I = dextrin residue 11 = 

 dextrin residue 111= isomaltose = glucose. 



(8) That all the products obtained from starch lay hydrolysis are to be designated dextrins. 



Those which originate by carbinolhydrolysis, and which do not reduce Fehling's solu- 

 tion he terms amylodextriu. The dextrin which originates from amylodextrin after 

 the splitting off of all the isomaltose molecules he names grenzdextrin. All dextrins 

 between amylodextrin and grenzdextrin, those therefore from which isomaltose can be 

 split off, he names maltodextrin. The dextrin which originates from grenzdextrin by 

 the splitting off of glucose he names glucodextrin. (See pages 118, 135, and 147.) 



In studies of the saccharification of starch by the amjdase of malt, Pottevin (Compt. 

 rend., 1898, cxxvi, 1218) dissents from the view of Brown and Morris that dextrin and 

 maltose are formed coincidently and not successively, and that all dextrins have the same 

 composition, molecular weight, rotatory power, and reducing power; but he supports 

 Duclaux in the theory that dissimilarities of dextrins are due to physical differences. By 

 heathig malt extract for 20 minutes at 79 to 80, and treating starch-paste with it, the 

 paste was liquefied quickly, the greater part going over into dextrin without forming any 

 reducing .sugar. The paste was prepared by subjecting 10 grams of starch in 1 liter of 

 water for half an hour at a temperature of 90, and then for the same length of time in an 

 autoclave at 120. The paste thus obtained was sufficiently transparent to allow of the 

 determination of its rotatory power, (a)j = -1-197.6. 



Two liters of the paste were treated with 30 c.c. of the heated malt extract at 60 for 

 12 hours. Allowing for the correction required by the malt, the rotatory power was un- 

 changed. A small quantity of iodine gave a violet reaction ; but with an adchtional amount 

 of the reagent the color became a reddish-brown. The fluid was concentrated until it 

 contained 10 per cent of solids, and it was then fractionally precipitated with alcohol. 

 A 63 per cent alcohol precipitated a dextrin that was colored blue at first and then brownish- 



